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Abstract:

The invention relates to a method for the anti-erosion coating of the wall
of a cyclone for separating and recovering solid particles driven in a
fluid, in which a composite material is deposited in a mould comprising
the wall of the cyclone (13) and an adapted form (17) in order to obtain,
upon stripping, an impression having a predetermined geometry, at least
one means for attaching the composite material to the wall of the cyclone
(15), and connected to said wall, is provided before casting in the body
of the impression. The invention also relates to an anti-erosion coating
for a cyclone inner wall that includes a composite material provided in
the form of a continuous layer on the inner wall of the cyclone, and at
least one attachment means connected to the wall of said cyclone in the
body of the coating, particularly with a smooth exposed surface. The
invention also relates to a cyclone including such a coating and to the
use of said coating.

Claims:

1. A process for the anti-erosion coating of a wall of a cyclone (1) for
separating and recovering solid particles entrained by a fluid,
characterized in thata composite material is placed in a mold comprising
the wall of the cyclone (13) and a suitable casing (17) in order to
obtain, upon stripping, an impression of defined geometry, andat least
one means for attaching the composite material to the wall of the cyclone
(15), joined to said wall, is placed in the thickness of the impression
prior to casting.

2. The process as claimed in claim 1, characterized in that the wall (13)
is an internal wall of the cyclone.

3. The process as claimed in the previous claims, characterized in that
the composite material is a composite construction material, preferably
concrete.

4. The process as claimed in claim 3, characterized in that the concrete
is a self-flow concrete.

5. The process as claimed in claims 3 and 4, characterized in that the
Al2O3/SiO2 ratio of the self-flow concrete varies from 9
to 12 and preferably from 10 toll.

6. The process as claimed in the previous claims, characterized in that
metal needles are added to the self-flow concrete.

7. The process as claimed in claim 6, characterized in that the proportion
of metal needles in the concrete varies from 0.1 to 5.0 weight %, and
preferably from 0.1 to 3.0 weight %.

8. The process as claimed in claims 6 and 7, characterized in that the
length of the needles ranges from 30 to 80% and preferably from 50 to 80%
of the thickness of the anti-erosion coating.

9. The process as claimed in claims 6 to 8, characterized in that the
diameter of the needles ranges from 0.1 mm to 1.0 mm and preferably from
0.2 mm to 0.7 mm.

10. The process as claimed in the previous claims, characterized in that
the thickness of the anti-erosion coating (18) varies from 10 mm to 100
mm and preferably from 10 to 50 mm.

11. The process as claimed in the previous claims, characterized in that
the anti-erosion coating is anchored to the metal wall by at least one
attachment means, for example at least one metal V (15), placed in the
thickness (18) of said coating.

12. The process as claimed in claim 11, characterized in that the height
of the V (15) varies from 50% to 80% and preferably from 60% to 75% of
the thickness of the anti-erosion coating.

13. The process as claimed in claim 11, characterized in that the number
of V's (15) varies from 10 to 100 per m2 and preferably from 10 to
60 per m.sup.2.

14. An anti-erosion coating for an internal wall of a cyclone comprising a
composite material, which is a self-flow concrete comprising an
Al2O3/SiO2 ratio varying from 9 to 12, positioned in a
continuous layer on the internal wall of the cyclone and at least one
attachment means joined to the wall of said cyclone in the thickness of
the coating, with in particular a smooth exposed surface.

15. The anti-erosion coating as claimed in claim 14, characterized in that
the coating consists of a composite material which is a self-flow
concrete comprising an Al2O3/SiO2 ratio varying from 9 to
12, positioned in a continuous layer on the internal wall of the cyclone
and at least one attachment means joined to the wall of said cyclone in
the thickness of the coating, with in particular a smooth exposed
surface.

16. The anti-erosion coating as claimed in claim 13 or 14, characterized
in that it is obtained as claimed in any one of claims 1 to 13.

17. A cyclone (1), characterized in that it contains a coating as defined
in any one of claims 14 to 16.

18. The cyclone (1) as claimed in claim 17, characterized in that it is
almost totally coated internally, that is to say at least 95%, in
particular at least 99%, or at least 99.9% of the internal surface, or
totally, by a coating as claimed in claim 14 or 15.

19. Use of a coating as claimed in any one of claims 14 to 16 for coating
an internal wall of a primary or secondary cyclone (1), in particular of
Fluid Catalytic Cracking.

Description:

[0001]The present invention relates to a process for the anti-erosion
coating of a wall, generally comprising a solid material. It also relates
to an anti-erosion coating, in particular obtained with this process, and
the use of this coating.

[0002]The invention relates in particular to a process for the creation of
an anti-erosion coating of a wall of a cyclone, a device for separating
and recovering solid particles entrained by a fluid.

[0003]More precisely, the invention relates to a process for creating an
anti-erosion coating on a metal wall, the anti-erosion coating obtained
with this process, and the use of such a coating when it is applied onto
the internal wall of a cyclone, generally used in the field of refining
and petrochemistry, in particular in a Fluid Catalytic Cracking (FCC)
unit.

[0004]It is to this application of FCC that reference will more
particularly be made in the remainder of the present description, but the
process which is the subject of the invention applies to all types of
solid wall, whatever its shape, onto which it is useful to apply
protection to avoid destructive erosion, for example due to the impacts
of solid particles entrained at high speed by a fluid or more generally
due to all types of impact, whatever their origin, onto a solid wall.

[0005]Fluid bed catalytic cracking (FCC) is a chemical process frequently
used in oil refineries, whose purpose is to convert heavy cuts of
long-chain hydrocarbons, for example derived from the distillation of oil
under vacuum, into lighter and more upgradable cuts. A high temperature
associated with the presence of a specific catalyst and a slight
overpressure relative to atmospheric pressure make it possible to crack
(break) the large hydro-carbon molecules so as to produce smaller
molecules representing a substantial upgrading, for example in the oil
product production chain.

[0006]The catalyst generally used is a zeolite with cationic substitutions
of rare earths maintained within an amorphous silica-alumina matrix.
Owing to the extremely small dimensions of its granules (of the order of
about fifty microns), said catalyst can be set in "fluid" or
"quasi-fluid" motion in the FCC.

[0007]In the FCC process, the feed to be processed and the catalyst are
introduced together into a reactor whose temperature can reach several
hundred degrees centigrade, for example 500° C. The effluents
formed in the course of the chemical reaction are freed from entrained
catalyst in one or more cyclones positioned in the upper part of the
reactor, and are then passed into a fractionating column.

[0008]The chemical reaction produced in the reactor of the FCC results in
the formation of deposits of coke on the catalyst. This necessitates
continuous regeneration of this catalyst. It is for this purpose that
there is provided in the FCC, continuously, a flow of the coked catalyst
towards a regenerator into which combustion air is blown at a temperature
of about 700° C. to burn the coke. The catalyst thus regenerated,
which can be classed as a new catalyst, is then reinjected into the fresh
feed at the inlet of the reactor.

[0009]It is this continuous and fluid motion of regeneration of the
catalyst which gives its name to the FCC process.

[0010]Although the catalyst freed of its coke is continuously removed at
the bottom part of the regenerator, there are non-negligible quantities
of solid particles of said catalyst which are entrained at the top outlet
of said regenerator by the combustion gas containing in particular carbon
dioxide (CO2), nitrogen (N2) and carbon monoxide (CO). This
combustion gas is next treated by various means in energy recovery units
to lower its temperature, then it is ejected via the chimney. It is
extremely important that the particles of catalyst be almost totally,
indeed totally, absent from this combustion gas, which requires the
presence of a device suitable for the separation and recovery of these
particles at the top outlet of the regenerator. In the same manner as in
the reactor and for the separation of the particles of catalyst with the
effluents formed during the cracking reaction, at least one cyclone is
used in the regenerator, preferably two primary cyclones installed in
series with two secondary cyclones, to separate and recover the particles
of catalyst contained in the combustion gas.

[0011]These cyclones thus have a primary role in the catalytic cracking
process, in particular with regard to the quality of the effluents
leaving the reaction zone and/or for the treatment of the combustion gas
leaving the regenerator, thus making it possible in this latter case to
ensure very low or even zero pollution by the catalyst on the emergence
of this said combustion gas from the chimney.

[0012]In an FCC, certain cyclones, which are static devices making it
possible to separate and recover the solid particles of catalysts
entrained by a gas flow and functioning on the double vortex principle,
can present the problem of undergoing erosion. In fact, their metal walls
being constantly exposed to the impacts of these particles endowed with
considerable energy, erosion phenomena can occur, and in extreme cases,
during the period of operation of the cyclone, result in perforation of
the steel of which it consists, for example stainless steel 304 H.

[0013]In fact, without wishing to be bound by this theory, it is possible
that in such cyclones the particle-laden gas arriving at a speed which
can attain several tens of meters per second, for example 15m/s to 30 m/s
in the inlet of said cyclone (referred to in the profession as the "ear"
or "mouth") owing to the geometry of that cyclone forms a vortex which
contributes energy to the various impacts of the solid particles of
catalyst against the internal walls, thus creating undesired erosion, in
particular in the mouth of the cyclone, on the body of the cyclone, the
dust pot and even the diplegs. This erosion can lead to one or more
perforations.

[0014]The perforation of a wall of a cyclone can cause major disturbances
in the functioning of the FCC, at first causing undesired emissions of
solid particles of catalysts into the atmosphere, which may in the end
necessitate shutdown of the FCC.

[0015]Solutions have been proposed in the prior art with the aim of
retarding, minimizing or indeed avoiding this erosion on the internal
walls of cyclones, by providing these internal walls with a specific
anti-erosion coating.

[0016]Thus U.S. Pat. No. 4,943,544 discloses the composition of a
refractory composite material of high quality which has low porosity,
high density and good mechanical strength as well as high resistance to
erosion. This material is intended to protect any surface which has to
exhibit high resistance to erosion and low thermal conductivity. The
process for obtaining this type of protection, in particular that which
makes it possible to protect the mouth and body of the cyclone, the
chimney, dust pot or indeed the diplegs, is not indicated in that
document.

[0017]Many devices, made of metal or composite materials, for anchoring
the anti-erosion coating on an internal metal wall are described in the
art and in particular in WO 97/03 322, U.S. Pat. No. 6,887,551, U.S. Pat.
No. 6,374,563, U.S. Pat. No. 4,753,053, U.S. Pat. No. 4,680,908, U.S.
Pat. No. 4,660,343 and U.S. Pat. No. 4,581,867. These anchoring devices
all have their particular features of shape and functioning with one same
objective, that of ensuring the anchoring of the anti-erosion coating on
its support, generally a metal wall.

[0018]The anti-erosion coatings generally installed today in catalytic
crackers, and more precisely on certain internal walls of the cyclones,
are made up of a hexagonal metal mesh deployed in the form of a honeycomb
called Hexmetal® and marketed for example by Causeway. The hexagonal
mesh, made up of cells whose internal dimensions can vary from 4 to 6 cm
for a thickness of about 1.5 to 3.0 cm, is multipoint welded onto the
wall to be protected so as to coat the whole of the internal wall of the
cyclone. The mesh is thus anchored on the wall by a series of welds of
the cells, say one cell in two. The various welds are made by specialised
personnel, generally on a removed or partially removed cyclone. The cells
are filled with composite material, generally concrete, by said personnel
manually with the thumb and smoothed with a trowel. This manual operation
is rendered necessary by the need not to trap air between the inner wall
and the concrete. In fact, in view of the operating temperatures of the
cyclone, the presence of air could by expansion cause the concrete-filled
mesh to explode or create craters, after partial erosion, favorable to
the generation of turbulence harmful to the good functioning of the
cyclone. This condition is so important that a pneumatic hammer is
sometimes used to tamp the concrete at the bottom and into its cell.

[0019]The fitting time for this coating technique in general lies between
1 and 3 hours per m2.

[0020]Moreover, in view of the internal narrowness of the cyclones, the
welding operations, and indeed cutting out by means of a grinding wheel
within this, are rendered delicate and difficult, including those of
filling the cells with the concrete, particularly having regard to the
corrosivity of this latter material.

[0021]In spite of this type of anti-erosion coating previously described,
it can happen that the metal wall of a cyclone (the primary cyclone)
perforates, after prior total erosion of the concrete and of the
Hexmetal®. This can occur after 4 to 5 years of continuous operation.
When secondary cyclones are present in the plant, such perforation, de
facto resulting in an overload of solid particles of catalyst in the
other cyclones, can result in the perforation of these secondary
cyclones.

[0022]Other erosion phenomena can occur during the period of operation,
for example preferential erosion by the solid particles of catalyst on
the metal mesh (the thickness) of the Hexmetal®, this thickness of
metal mesh being located at the junction of two cells filled with
concrete. This erosion, once established, promotes the attrition of the
concrete in the adjacent cells, and can lead to the total disappearance
of the concrete and then, on completion of the erosion, to perforation of
the metal wall.

[0023]On shutdown of the plant, it is then necessary to replace the
concrete and the Hexmetal®. This can for example be done by
hydro-demolition of the concrete, chipping out the Hexmetal®,
smoothing the walls with a grinding wheel and cleaning, installation
(welds) of a new Hexmetal®, loading the concrete by hand, etc. The
removal of the Hexmetal® can also be effected by grinding, but this
work is rendered hazardous to the personnel, in particular owing to the
narrowness of the interior of a cyclone.

[0024]The time for removal of damaged Hexmetal® from a cyclone,
normally encountered in a catalytic cracking unit, is generally more than
15 days, while the time for installing new Hexmetal® including the
loading thereof with concrete is estimated at about one month for a
cyclone of average size normally encountered in FCC units.

[0025]It thus follows that many disadvantages are associated with this
type of coating, among them: [0026]the difficulty of installing
Hexmetal® on the metal wall due to the need to perform many welds,
[0027]the difficulty of manual introduction of the concrete into each of
the cells formed in the Hexmetal®, [0028]the implementation time by
specialized personnel for carrying out the tasks described above,
[0029]the qualification of the personnel for this type of site, [0030]the
cost resulting from possible removal of a coating eroded during a
previous operating cycle, to which must be added that of the installation
of the new coating as defined above, and [0031]the substantial
expenditure which must be added to those inherent in the replacement of
an anti-erosion coating, namely the loss of revenue to the operator
during the intervention period.

[0032]Apart from this, the installation of an anti-erosion coating made up
of Hexmetal® and a suitable cell-filling concrete in accordance with
the good practice of the profession is not a guarantee of performance
over time since it is not uncommonly observed that for certain cyclones,
particularly secondary ones, the metal wall may be perforated after local
total erosion of the coating, this occurring after 4 or 5 years of
operation or even 3 years.

[0033]In the course of many studies in this field, the Applicant has
attempted to remedy the problems described above wholly or in part by
modifying the nature of the coating and by proposing an application
process not usual for this type of installation.

[0034]According to one aspect, a subject of the present invention is a
process for anti-erosion coating of a wall of a cyclone for separating
and recovering solid particles entrained by a fluid, characterized in
that a composite material is deposited in a mold comprising the wall of
the cyclone to be protected from erosion and a suitable casing, in order
then to obtain on stripping an impression of defined geometry, and in
that at least one means of attachment of the composite material to the
wall of the cyclone, joined to said wall, is placed in the thickness of
the impression prior to casting.

[0035]The process which is a subject of the present invention applies to
the anti-erosion coating of any wall, in particular of a cyclone and more
generally on any metal wall a face whereof must be protected from an
aggressive, in particular mechanically aggressive, agent. This process is
in particular of enormous interest for the coating of at least one
internal wall of a cyclone, in particular installed in a fluid catalytic
cracking unit for hydrocarbons.

[0036]The composite material, in the sense of the present invention, is
preferably a material resulting from combination of at least two
non-miscible materials having a strong adhesive capacity. Preferably, the
composite material is a composite construction material such as concrete,
and still more preferably a concrete of the self-flow type.

[0037]This self-flow concrete can have an Al2O3/SiO2 ratio
calculated on a calcined basis ranging from 9 to 12 and preferably from
10 to 11, and physicochemical properties such that it flows naturally
into a mold without the need to use a vibratory system to ensure its flow
into the various parts of said mold, even if the latter includes
particular places necessitating non-forced filling in the direction
opposite to gravitation.

[0038]By way of example, such a concrete is the ACTCHEM 85 Trueflow
concrete distributed by Dramicon, also referred to below in the present
description as "self-flow concrete". This self-flow concrete gives
mechanical performance results according to the standard ASTM 704/A
704M-06 one to three times better than other concretes normally used for
anti-erosion coatings.

[0039]According to a preferred implementation mode, the composite
construction material further contains metal needles to reinforce its
mechanical performance and limit any microfissures in it. Identical or
different, for example straight or omega-shaped, the needles can have an
overall length ranging from 30 to 80% and preferably from 50 to 80% of
the thickness of the anti-erosion coating, and a diameter which can vary
from 0.1 mm to 1.0 mm and preferably from 0.2 mm to 0.7 mm.

[0040]In the sense of the invention, "needle" is understood to mean a fine
metal rod made of a steel, preferably stainless, and more or less pointed
at its extremities, distributed for example by IRIS.

[0041]Preferably, the needles are mixed with the concrete, in particular
self-flow concrete, in a proportion ranging from 0.1 to 5.0 weight % and
preferably from 0.1 to 3.0 weight % relative to the total weight of the
concrete.

[0042]The shape of the mold is calculated and executed for excellent, or
even perfect, obtention of the finished product on stripping, in other
words in the case of the present invention, of the desired shape and
thickness of the anti-erosion coating, one of the faces of the mold
consisting of the wall to be coated.

[0043]The thickness of the anti-erosion coating, in other words the
distance separating two parallel faces of the mold, ranges from 10 to 100
mm and preferably from 10 to 50 mm.

[0044]The person skilled in the art with full knowledge of the facts will
adapt the various construction constraints of this mold, in particular
its make-up of several elements, for easy stripping.

[0045]The mold can be made of any hard material, preferably metal, and
still more preferably of steel.

[0046]Any shape can be given to the anti-erosion coating by the creation
of a specific mold, which by the obtention of a suitable impression on
stripping, can make it possible to modify the interior shape of a cyclone
simply without interfering with its initial construction profile.

[0047]The attachment means can take on multiple shapes, with 2, 3, 4, 5, 6
or more extremities, and for example be in the shape of an X, V, T, Y,
etc.

[0048]In one implementation mode of the invention, the attachment means,
in other words the means of anchoring the anti-erosion coating to the
wall to be protected, is a V the bent part whereof is fixed, generally by
welding onto the wall, this V being placed in the thickness of the mold
prior to the pouring of the concrete, in particular self-flow concrete,
it will thus finally be located in the thickness of the coating.

[0049]Preferably, this attachment V is metallic and is made of a steel of
the stainless 304 H type, and its height measured perpendicular to the
internal wall can vary from 50% to 80%, and preferably from 60% to 75% of
the thickness of the anti-erosion coating. Its diameter can vary from 4
to 10 mm and preferably from 4 to 8 mm.

[0050]At least one attachment V is necessary to anchor the anti-erosion
coating to the wall to be protected, but it will be preferred to
position, prior to casting, several V's per unit area of the wall to be
protected. Thus the number of V's can vary from 10 to 100 per m2 and
preferably from 10 to 60 per m2.

[0051]The invention also relates to an anti-erosion coating for a wall of
a cyclone comprising a composite material positioned in a continuous
layer on the internal wall of the cyclone and at least one attachment
means joined to the wall of said cyclone in the thickness of the coating.
In particular, the exposed surface is smooth.

[0052]Of course, the coating can be obtained following the implementation
process and/or with the constituents previously described.

[0053]In contrast to the use of Hexmetal®, where there are
discontinuities between the various cells filled with composite material,
these discontinuities being due to the thickness of the metal making up
the Hexmetal®, the anti-erosion coating according to the invention is
placed by casting in a continuous layer without any discontinuity. As a
result, and because of the molding technique, the surface of the concrete
exposed to the solid particles is even, and preferably smooth.

[0054]According to a further aspect, a subject of the invention is a
cyclone containing a coating according to the invention.

[0055]In particular, the cyclone is internally coated almost totally, that
is to say at least 95%, preferably at least 99%, or even at least 99.9%
of the internal surface, or totally, with a coating according to the
invention.

[0056]The invention thus relates to the use of such a coating for coating
at least one internal wall of a primary or secondary cyclone, in
particular in a Fluid Catalytic Cracking unit of an oil refinery.

[0057]The present invention is explained in more detail by means of FIGS.
1 to 2 representing one implementation mode of an anti-erosion coating
for an internal wall of a cyclone, in particular the internal wall of the
body and the chimney of an FCC cyclone.

[0058]In this description, reference will be made to the attached drawings
wherein:

[0059]FIG. 1 is a general diagrammatic view of a cyclone used in an FCC
according to the invention.

[0060]FIG. 2 is a diagrammatic view of the coating, in the casting
process, of parts 2, 3 and 8 of the cyclone represented in FIG. 1.

[0061]FIG. 1 is a general diagrammatic view of an FCC cyclone according to
the invention. The cyclone 1 comprises an inlet mouth 3 for a mixture of
solid particles (here particles of catalyst) and of gas, and the body of
the cyclone properly speaking 8, of essentially cylindrical shape, joined
to a lower part 4, of conical shape splayed towards the top. This conical
part 4 opens into a dust pot 5, also of essentially cylindrical shape,
itself joined to a lower part 6, of conical shape splayed towards the
top. This second conical part is joined to a lower part 7 (dipleg),
essentially cylindrical, which makes it possible to recover the solid
particles. The body of the cyclone 8 contains a chimney part 2 by which
the gases emerge, in the upper part. The operating principle of the
cyclone is that the mixture of particles and gas, arriving at very great
speed via the inlet mouth 3, start a very rapid rotating motion in the
body of the cyclone 8, said motion extending as far as the parts 4, 5, 6
and 7. Two vortices are thus created in the cyclone, one rising of low
density corresponding to the gas and another descending of higher density
corresponding to the particles. These particles then fall into the leg 7,
while the gases emerge via the chimney 2.

[0062]In the profession, it is usual to refer to: [0063]parts 3, 8 and 4
as the "body of the cyclone", [0064]part 2 as the "chimney", [0065]parts
5 and 6 as the "dust pot" and finally [0066]part 7 as the "dipleg".

[0067]FIG. 2 is a diagrammatic view of an arrangement of a mold for an
operation of casting a self-flow concrete according to the present
invention. In this case, the part 8 incorporating the parts 2 and 3 of
the cyclone has been dismantled (unsoldered), inverted then placed on a
flat surface. The mold was made up of at least one external assembly 17
(only the internal face of the mold complementary to the wall to be
coated is shown in FIG. 2) making it possible to dimension the desired
impression, in other words its shape and its thickness 18 here equaling
25 mm. V's are placed on the internal wall 13 to be protected, and serve
for the attachment (anchoring) of the concrete onto the wall 13. Here the
V's are all identical, and each comprise two solid essentially
cylindrical parts, forming an angle essentially equal to 90° to
one another. The height of the V's lies between 15 and 20 mm and the
diameter of each of the two essentially cylindrical parts lies between 5
and 8 mm. They were attached to the wall 13 by welding at their bent part
and they number 50/m2. The use of the self-flow concrete, here
Actchem 85 Trueflow to which 0.5 weight % of omega-shaped needles had
been added make it possible during casting progressively to fill the
spaces created by the mold along the internal wall of the part 8 of the
cyclone, then the bottom, and finally, by the concrete rising, the walls
of the chimney 2.

[0068]After stripping, the self-flow concrete is baked according to the
good practices of the profession, in order to place it, prior to its
final mounting in the FCC, under temperature conditions normally
encountered in the operating cycle of an FCC cyclone.

[0069]Whereas it used to require about a month and a half to reconstitute
the anti-erosion coating of an eroded FCC cyclone of average size, with
specialized personnel, involving risks due to the use of specific
equipment, welding and wheel-grinding in a confined space (the interior
of the cyclone), the use of the invention makes it possible to divide by
at least 2 the immobilization time of said cyclone while minimizing the
aforesaid risks to the personnel.

[0070]Moreover, because of the absence of Hexmetal® to be installed,
the present invention is of great interest in the possible replacement of
the anti-erosion coating, according to the present invention.